What name is given to the rate at which velocity changes?

acceleration

Explanation:

Acceleration is used to describe the rate at which velocity changes. Speed is another way to say velocity, so a gain or a loss in speed is also known as acceleration.

So, acceleration can be negative or positive. It is positive if velocity is gained (increased) and negative if velocity is lost (decreased).  

2,407.2 miles. or 32 hours.